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24 Sep 2013:
Major Wind and Rain Belts Could Shift North as Earth Warms

A study of warming at the end of the last Ice Age indicates that future warming caused by the burning of fossil fuels will likely shift the planet's rain and wind belts northward, say researchers at Columbia University's Lamont-Doherty Earth Observatory. Regions that are already dry — including the western U.S., western China, and the Middle East — could grow drier, while equatorial Africa and monsoonal Asia may become wetter. An examination of data such as polar ice cores and ocean sediments shows that as the last Ice Age ended 15,000 years ago, northward shifts in the tropical rain belt and mid-latitude jet stream occurred as the temperature gradient between the northern and southern hemispheres increased. That sharper gradient came about because the land mass-dominated northern hemisphere warmed faster than the ocean-dominated southern hemisphere, according to the study, published in the Proceedings of the National Academy of Sciences. Researchers say a similar pattern could develop in years to come as the northern hemisphere continues to warm faster than the southern hemisphere. Although there is not yet clear evidence of increasing circulation in the North Atlantic Ocean or strengthening monsoons in Asia, those effects could begin to emerge as air pollution — particularly sulfate aerosols, which can temporarily mask some effects of climate change — declines in the northern hemisphere.

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